bison interpreterext.ypp # to create C++ file interpreter.tab.cpp
bison -d programext.y # to create header file program.tab.h for lexer
flex programext.l
gcc -c lex.yy.c # create the object file lex.yy.o
g++ interpreterext.tab.cpp programext.cpp lex.yy.o -o interpreterext # compile and link  
